Solar in the Winter?

wildebus

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I thought I would post a little comparision to show the difference in the solar harvesting that can be expected at different times of year. My vehicle hasn't changed in terms of Batteries and Solar Panels (440Ah/400W) and the vehicle would have been parked in exactly the same place give or take a foot or so. (My parking location is not that good for solar, but that is true of the Summer as well as the Winter).
These charts show a seven day period of Solar Harvesting (Orange) and Consumption (Pink)
(the blue line shows the daily average battery SOC and the shading is the upper and lower SOC for the day)

So this month of November:

WinterSolar
by David, on Flickr
So in the week above the peak harvest provided about 16.5Ah for the entire day


Going back to July we see this chart:

SummerSolar
by David, on Flickr
The first 2 days we are getting in excess of 180Ah each day, and the only reason the other days have dropped is the batteries are already full by around midday so the solar harvesting will just be covering consumption demands and any excess wasted.


So a pretty dramatic difference between the two months there, with November being just 10% of the performance of July! Different areas of the country will be a bit different of course, and especially if in Southern Europe, but I think it shows attempting to rely on Solar in the winter is a tough ask.
 

maingate

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If you have roof mounted panels then it's not surprising. A tilted panel makes a huge difference in Winter. With a freestanding 90 Watt panel, I have harvested 4 Amps at 10 am on a bright, cold February morning. A flat panel would have been producing about one third of that.

A few years ago I drew up an idea for utilising a rear mounted cycle rack and converting it into a Solar panel mount for a couple of 100 watt panels. I reckoned that with an appropriately parked orientation, it would extend off grid parking substantially in Winter.
 

wildebus

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Very few people have tiltable panels though. This is a real world like-for-like comparison of the two time periods.

Tilted panels in the summer would also have a big effect - and I would venture actually more so than in Winter as the 'solar day' is so much longer.
 

jagmanx

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November at 10% of July is about right
I have solar panels on my house which feed into the Grid.
Thus all the power is harvested. for a few years I tracked the figures weekly
Not surprising really
  • Less hours (that in itself would bring the figure down to 40%) then....
  • Sun lower in the sky
  • More clouds
a "triple Whammy" and maybe more..
As you suggest
In the summer you do not need tilting
In the winter it wont help much..even if you were to get double (Double of nothing is nothing)
 

nabsim

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Very few people have tiltable panels though. This is a real world like-for-like comparison of the two time periods.

Tilted panels in the summer would also have a big effect - and I would venture actually more so than in Winter as the 'solar day' is so much longer.
maybe not in real terms as batteries are usually ful before lunch time anyway in the summer but I know what you mean :)
 

wildebus

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maybe not in real terms as batteries are usually ful before lunch time anyway in the summer but I know what you mean :)
Depends what you do with your batteries? e.g. Induction Hob in the morning to make Breakfast; Use Slow Cooker during day to cook evening meal; Have the Hot Water fully charged by mid afternoon; Induction Hob for night time munchies or drinks.
So all free power :)
 

nabsim

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Easy one Dave, in summer the fridge :)

Oh and maybe an odd light later on, well not quite, we charge phones, tablets and watches. Will attempt the mobility scooter again in good weather but definitely not on a dull day ;)
 

maingate

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I used a tilted solar panel 'in the real world' for a long time and still do occasionally. My current van is the first one I have owned with a roof mounted panel. On the temporary holiday sites I use, there are many in use, mainly caravanners but also motorhomes too.
 
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nabsim

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I used a tilted solar panel 'in the real world' for a long time and still do occasionally. My current van is the first one I have owned with a roof mounted panel. On the temporary holiday sites I use, there are many in use, mainly caravanners but also motorhomes too.
I meant for me Jim, in summer my roof mounted panels provided what we needed except for Burtonwood but that was because I left scooter batteries charging and forgot they were on charge :(

I have seen you (and others) with your folding panel and considered them for poorer weather conditions but I can’t see any options of keeping batteries up indefinitely over winter apart from EHU or a generator for us. It’s all downhill if you can’t start off with full batteries from what I can see but still looking and considering
 

maingate

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When I use the van in Winter Neil, I stick to wildcamping etiquette and move on every day. A mix of solar and alternator charging extends the offgrid experience .... but not for any great length of time. :( One night on a small Site and off we go again. :)

A greater worry for me is the LPG availability as my heating gets through a fair bit of gas.

I should also add that I carry a small 10" TV for Winter use which uses no more than 1 amp per hour as opposed to around 3 times that of my 19" TV. That means the short days and longer nights are not a huge drain on my batteries.
 

wildebus

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I used a tilted solar panel 'in the real world' for a long time and still do occasionally. My current van is the first one I have owned with a roof mounted panel. On the temporary holiday sites I use, there are many in use, mainly caravanners but also motorhomes too.
Lots do. But the GREAT MAJORITY don't. And if you tilted them in the winter, you would tilt in the summer as well. My post was about comparing the seasons, not commenting about absolute harvesting. (And the post from jagmax ref his house setup confirms that difference).

Yes, tilting will gain you more obviously, but how much more? Well, reckoned to to be about 40-50% more I think? So in MY setup, I would gain this month maybe 8Ah a day. Woo hoo! And someone with say 200W rather than 400W? 4Ah. That's 4Ah - A DAY! If you started your engine for 5-10 minutes you would put more than 4Ah into your battery from a reasonable split-charge system.
Is working out the best position to park for your panels to tilt them, getting on the roof, putting them up, etc, etc, really worth 4Ah? Maybe for some...
Now in the summertime, where that 40% bonus can bring in upto 40Ah extra (upto 80Ah in my case), tilting becomes a much more worthwhile proposition and the effort provides useful returns.
 

maingate

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Who reckons only 40% more? I think you will find at these Northern Latitudes it is considerably more than that. In fact I know for a fact it is a lot more. I know because I had an ammeter fitted to the solar wiring and could compare different angles at different times of the year. I started with the panel flat in order to get a base reading and tried different angles to find the maximum input.

4 amps from 10 am through to 3 pm is 20 amp/hours by my reckoning with a 90 watt panel. Or to use your example with 200 watts of solar, it would be over 40 amp/hours ...... woo hoo indeed.
 

maingate

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What can't speak, can't lie (and I don't like being called a liar on an open forum) .....

....... I am not going to argue with you. You techo whizzkids think you know everything ... I'm out.
 

wildebus

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One of the biggest issues with Solar nowadays in the home is that all the shisters who used to sell Double Glazing moved into the Solar Energy Industry once DG became more regulated. I remember door knockers saying with the Solar DHW systems that you would have so much excess hot water you could feed your heating system with it! Yeah, right on that one.
I did install Solar DHW (actually a lot more efficient value wise than PV Panels a decade ago) with my own design setup and it WAS great - teamed it up with a specific european Combi-Boiler that accepted warm water feed-in (most UK market Combis didn't then) and the boiler wasn't needed for most of the summer - and in the winter, the energy it used was the same as a standard Combi in the summer with the pre-heated water in. I used to have a data logger on the system (surprise surprise!) and was able to calculate the ROI on the system to be under 5 years (a Solar PV system even today with cheaper panels and current tariff buy-back is typically measured in decades in terms of ROI)
Dec 08/Jan 09 was a cold time on the south coast and the mains water was very cold indeed. This is the water temp in the Thermal Store, heated solely by solar (and of course heat being used daily for showers, washing etc, so needing to be replenished)

Solar-DecJan
by David, on Flickr
 

jagmanx

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ROI Solar Panels (PV with feed in Tariff)
Installition in July 2011 about £10,000 including a new Meter consumer unit.
To date my return has been £10,700 so 7 years
Or Income about £1200 a year so 12 % of course the capital has "gone" and I suspect it will have little impact when I come to sell
 

wildebus

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ROI Solar Panels (PV with feed in Tariff)
Installition in July 2011 about £10,000 including a new Meter consumer unit.
To date my return has been £10,700 so 7 years
Or Income about £1200 a year so 12 % of course the capital has "gone" and I suspect it will have little impact when I come to sell
That's a pretty decent result there. I recall the feed-in tariffs were insanely good (upto 30p/unit?) for a while - did you manage to get onto one of those deals? I would think having a system would be a definate bonus for selling - but having said that, my Solar DHW system didn't seem to excite anyone when I had my house up for sale (except the Energy Inspector, who really liked it).

I was reading a while back that in Australia, one of the best places for Solar Harvesting generally, there are a lot of changes occuring and people who are net energy providers (so generate more than they use overall) are getting charged to be connected to the grid to discourage Solar as the infrastructure cannot cope with the reverse power in during the day or something!
 

jagmanx

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Almost 50p a unit guaranteed for 25 years (from installation) plus inflation
Yes a very very good deal.
Before going for this we had a "Hot Water GUY" visit and bore us for 4 hours and offering a deal for maybe £9000 but ONLY £6000 if we signed up immediately !!!
No real benefit
No way and smacks of a DG salesman.
I read your post and seems to work out well for you
BUT I saw no tangible benefit and indeed no financial return !
 

wildebus

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Wow! 50p a unit (plus RPI)! And until 2036!! Now when you are selling, that must be a big plus point to anyone looking with their eyes open.

Solar DHW ... at the "doorstep" prices, it is very poor value I agree. I contacted a specialist company who installed the solar tubes and the pipework to the pump, then Pump to Store; but I installed all the rest - the Thermal Store, all the plumbing and the pipework upto the boiler tails myself.
Was well chuffed with the results I cannot deny. This was just after the Combi was fitted.

IMGP0496
by David, on Flickr
(I remember I used colored tywraps to make it easier to see what pipes went where - Blue is cold (mains), Red is Hot (to taps) and Green is Green Energy (solar heated)).
Thermal Store has coils for the Solar and the Rayburn (as a heat dump), plus an immersion as a "just in case" and the combi is fed through it. The various lever valves allow any part of the system to get shut off and bypassed and the various auto-valves means the Combi will only ever come on when the water is below a set temp (think 43C from memory? Something to do with legionnaires) and the water is never above 60C as the TMV will open to mix as required.
It wasn't a massively cheap system, but because I had to replace the old boiler anyway, redo the heating pipes and radiators; change or lose the hot water tank AND do something about the massive rayburn radiator heat-dump in the dining room, getting a system that was "solar DHW ready" added little to the cost, and the solar install itself was not expensive (nowhere close to the Doorstepper prices)
 

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